Pressure equalization valve and switch

ABSTRACT

Apparatus for selectively venting a pressure-sensitive fluid system. Fluid pressure of the system is directed through a first conduit into a chamber having an expandable wall portion and through a second conduit which terminates in an opening adjacent and facing the external surface of the expandable wall. Small system pressure fluctuations are vented through the opening of the second conduit and large pressure changes cause the expandable wall portion to extend into sealing contact with the termination of the second conduit, thereby closing the vent opening. System fluid pressure may also be directed through a third conduit into a second expandable wall fluid chamber and the expansion of that wall utilized to actuate an electrical switch.

United States Patent Inventors Appl. No. Filed Patented Assignee PRESSURE EQUALIZATION VALVE AND SWITCH 5 Claims, 4 Drawing Figs.

[56] References Cited UNITED STATES PATENTS 266,462 10/1 882 Gordon et al [37/517 2,70! ,827 2/1955 Mathisen 200/83 N 3,349,559 10/1967 Gloor 60/62.5

Primary Examiner-R. F. Staubly Attorneys- Paul E. Harris and Lee R. Larkin ABSTRACT: Apparatus for selectively venting a pressure-sensitive fluid system. Fluid pressure of the system is directed through a first conduit into a chamber having an expandable wall portion and through a second conduit which terminates in an opening adjacent and facing the external surface of the expandable wall. Small system pressure fluctuations are vented [1.8. CI 200/83 E, through the opening of the second conduit and large pressure 49/264, 60/626, 137/5 l7, 200/83 N changes cause the expandable wall portion to extend into seal- Int. Cl ..II 0lh 35/40, ing contact with the termination of the second conduit, FlSb 7/00, Fl6k 2l/l6 thereby closing the vent opening. System fluid pressure may Field of Search 49/264, also be directed through a third conduit into a second ex- 265; 60/625,626 A; l37/498,5l7; 200/83 E, 83 pandable wall fluid chamber and the expansion of that wall N utilized to actuate an electrical switch.

27 H 26ml 4 3g 29 a J4 J5 l PRESSURE EQUALIZATION VALVE AND SWITCH RELATED APPLICATION This application is a continuation-in-part of US. application Se'r. No. 834,985, filed June 20, 1969, by the same inventors and entitled Pressure-Sensitive Fluid Signal System, now abandoned.

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a pressure equalization valve for selectively venting a pressure-sensitive fluid system.

2. Description of the Prior- Art In pressure-sensitive fluid systems it is frequently necessary to sense small sudden changes in pressure relative to the normal operating pressure. In many of these pressure systems this sensing is complicated'by the existence of small but generally continuous changes in the normal operating pressure of the' system. Over a period of time these small deviations in normal pressure may be cumulative and eventually may be sensed and indicated as the occurrence of a sudden pressure change. Variations from the normal system pressure which do not cumulate to activate the pressure sensor will nevertheless act as a bias upon the pressure sensor, changing its preset sensitivity.

The foregoing pressuresensing problem may occur in both pressure systems open to the atmosphere and in closed systems. A typical open fluid system monitoring problem is that of sensing the level of water in a tank to determine when sudden level changes occur. With a pressure sensor arranged to monitor the pressure of a column of water and set to detect sudden pressure changes, gradual evaporation of the water will eventually actuate the sensor and will cause an erroneous indication of sudden level change.

A typical closed fluid system situation exhibiting this problem of gradual change of normal pressure is found in the art of pressure pad object sensors. For example, in an automatic door-opener apparatus, a pressure pad containing a volume of air is located on the floor adjacent a door and a pressure sensor communicating with pad air is used to actuate an operator to open the door. This system must be responsive to sudden small pressure changes so that the weight of a small child or of an empty grocery cart will cause the door to open. Since the door must remain open for the duration of pressure on the pad, the fluid system must remain closed when pressurized. As a result, most of these air systems are designed to be permanently closed. Gradual fluid leakage from the system over a period of use will sufficiently desensitize these systems so that larger than desired pad pressures are required to actuate the pressure sensor. In addition, ambient temperature changes and atmospheric pressure changes can cause an increased system pressure. In a system originally provided with the proper air pressure, these increased pressures can be sufficient to cause unwanted actuation of the pressure sensor.

Prior art solutions to this problem in the pressure pad art suggest periodic venting of the fluid system with electrically actuated solenoid valves arranged to block venting during system operation. U.S. Pat. No. 3,349,559 is typical of the prior art. Prior art solutions are unduly complicated, however, and require an electrical power source for solenoid actuation. Also, these solutions are not suitable for a variety of applications where the problem of gradual changes in standard pressure arises.

SUMMARY OF THE INVENTION The pressure equalization valve of this invention provides for selective venting of a fluid pressure system and includes a first fluid conduit arranged for connection at one end of the pressure system, with the other end of the first conduit terminating in a fluid chamber having an expandable wall portion. A second fluid conduit is connected at one end to the first conduit, with the other end of the second conduit opening toward the external surface of the expandable wall.

Fluid pressure changes below a predetermined level may vent through the open second conduit, which opening is sealed by the expandable wall in response to pressure changes higher than the predetermined pressure level. A closure seat may be provided on the external surface of the expandable wall to insure proper closure of the second conduit and the second conduit may be provided with means for restricting fluid flow therethrough.

The invention may also include a third conduit connected at one end to the first conduit, with the other end thereof arranged to actuate an electrical switch in response to increased system fluid pressure. This switch may take the form of a second fluid chamber having an expandable wall portion and electrical contacts disposed adjacent the expandable wall and arranged to be actuated upon extension of the expandable wall.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a generally schematic view of a'fluid pressure pad system utilizing one embodiment of the pressure equalization valve of this invention.

FIG. 2 is a generally cross-sectional view of one embodiment of the pressure equalization valve of this invention.

FIG. 3 is a generally cross-sectional view of a second embodiment of the valve of this invention. FIG. 4 is a side view of the second embodiment taken along line 44 of F lg. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. I, there is illustrated an air pressure pad system including a doormat 10 having an air tube 11 embedded therein. An air tube 12 communicates pressure changes in the air in pad 10 to a pressure sensor switch I3 which includes a diaphragm 14 arranged to expand and actuate electrical switch 15. Closure of switch 15 will complete an electrical path across terminals 16 and 17 and may be used to energize a variety of circuits, such as an operator arranged to open a door. The pressure sensing and control circuit of Flg. I could also be used in controlling household appliances, industrial equipment, traffic signals and similar devices. The system of FIG. 1 is selectively vented by a first embodiment of this invention in the form of pressure equalization valve 18 connected to air tube I2 by air tube 19.

Valve 18 is shown in greater detail in FIG. 2 and includes a first air tube or conduit 20 communicating with tube 19 and terminating in an expandable fluid chamber 21.

The left-hand wall 22 of chamber 21 is formed of nylon and extends to the left in response to an increase in fluid pressure within chamber 21. Wall 22 should be considered as the expandable wall portion of chamber 21, even if that chamber is constructed with bellows-type sidewalls and a rigid left-hand wall, since, as described below, valve operation depends upon relative movement of wall 22.

A second conduit or tube 23 is connected on one end to tube 19 and the other end thereof terminates in an opening adjacent wall 22. An orifice 24 is provided on the termination end of tube 23 to restrict the flow of fluid therethrough. Sensitivity of valve 18 may be altered by changing the size of the opening in orifice 24 and, if desired, orifice 24 may be made adjustable. In the absence of a large pressure surge through tube 19, wall 22 will be retracted to the position shown in Fig. 2 and small fluid pressure changes in tube 19 will be allowed to vent through the open end of tube 23 and orifice 24.

Presence of a large pressure change in tube I9 will cause wall 22 to extend leftward into engagement with orifice 24 on the open end of tube 23, preventing tube 19 and the pressure system connected thereto from venting during theduration of the source of the pressure change. Removal of the pressure source will cause wall 22 to retract to its former position, al' lowing the fluid system to again vent. Wall 22 is assisted in returning to the retracted position by the force of coil spring 25 thereon. Spring 25 provides a bias to wall 22 and, in combination with orifice 24, allows precise preselection of the valve-operating pressure. By constructing chamber 21 or wall 22 of a high elasticity material, return bias for wall 22 inherently would be provided and spring 25 could be eliminated if the pressure selection function thereof is not required.

If a very low leakage seal is required between wall 22, when extended, and orifice 24, a valve seat 26 attached to wall 22 and arranged for movement therewith may be employed. Seat 26 may be constructed of latex rubber.

In operation, a force upon pad and tube 11 will cause an increase in air pressure in tube 11 which is communicated by tube 12 to switch 13 and from tube 12 through tube 19 to valve 18.

If this pressure increase is equal to or greater than the amount necessary to extend wall 22 and seat 26 against orifice 24, the system will be closed. Assuming this pressure is sufficient to extend diaphragm l4 and thereby close switch 15, the apparatus connected to terminals 16 and 17 will be actuated. No further change in the fluid system will occur until the force upon pad 10 is removed. At that time the pressure therein and in chamber 21 will decrease and wall 22 will move to the right and out of contact with orifice 24. This right-hand movement of wall 22, as viewed in FIG. 2, will be aided by the force of spring 25. Any change in system pressure less than that required to effect closure of orifice 24 by wall 22 will be vented through tube 23 and orifice 24.

Referring now to Flg. 3, a second embodiment of this invention is illustrated which may be used with pad 10 to replace valve 18 and switch 13 shown in FIG. '1, or may be used in a variety of other pressure-monitoring systems.

In this embodiment fluid from the system to be monitored and selectively vented is directed through tube 27 into the conduit 28 which is formed within valvebody 29. The left and right ends of the lateral portion 28a of the conduit 28 are enclosed by expandable diaphragms 30 and 31, respectively, which diaphragms are retained in position by rings 32 and 33, respectively. Diaphragms 30 and 31 are spaced a small distance away from valve body 29 by ring spacers 34 and 35, respectively, and form fluid chambers 36 and 37, respectively, with body 29.

Diaphragms 30 and 31 may be formed of latex rubber, or other resilient material which is relatively nonporous to the system fluid and which will extend outward from body 29 in response to a pressure increase within tube 28.

Since diaphragms 30 and 3] are formed of a resilient material, they will be inherently biased to return to the unextended positions shown in Fig. 3 upon removal of fluid pressure from the inside surfaces thereof. if it is desired to form diaphragms 30 and 31 of nonresilient material, additional positive biasing means, such as compression springs, should be added to effectuate diaphragm return.

Selective venting of the system fluid is achieved through conduit or tube 38 which is connected at one end to tube 28 and which terminates at the other end thereof in an opening directed toward the external surface of diaphragm 30. As illustrated in FIG. 3, an orifice 39 may be provided at the open end of tube 38 to restrict the flow of system fluid therethrough. As in the first embodiment, shown in Fig. 2, valve sensitivity may be adjusted by changing the size of the opening in orifice 39, and if desired, orifice 39 may be made adjustable. A mounting bracket 40 is provided to retain orifice 39 in a spaced relationship to diaphragm 30. A sufficient increase in system fluid pressure will cause diaphragm 30 to extend to the left and into engagement with the open end of orifice 39, preventing the system fluid from venting through tube 38. If desired, a valve seat plate 41 and valve seat 42 may be provided on the external surface of diaphragm 30, as shown, to assist in effecting closure of tube 38 upon increase in system fluid pressure.

In addition to the venting function performed by the valve of this second embodiment, means are also provided for generating an output signal in response to increases in system fluid pressure. A pair of electrical conductors 43 and 44, best seen in FIG. 4, are mounted on valve body 29 using insulators 45 and 46, respectively, and are positioned with their unsupported ends adjacent the central portion of the external surface of diaphragm 31. Conductors 43 and 44 are provided with contacts 47 and 48, respectively, which contacts are directed towards diaphragm 31. A contact plate 49 is carried by diaphragm 31 and is arranged to close the circuit through contacts 47 and 48 upon rightward extension of diaphragm 31 resulting from increase in system fluid pressure. Contacts 47 and 48 are threadably attached to conductors 43 and 44 so that the relative spacing between the contacts and plate 49 may be adjusted to alter switch sensitivity. if desired, a single conductor and contact could be utilized, with external electrical circuits connected between plate 49 and the single contact.

In operation the pressure equalization valve of this second embodiment is connected through tube 28 to a fluid system to be monitored. The size of orifice 39 and its spacing from seat 42 are appropriately selected to allow venting within the desired pressure range. The spacing of contacts 47 and 48 to plate 49 are likewise selected to allow circuit closure at the desired pressure level. In different situations, switch closure may be desired before, after, or concurrently with closure of orifice 39 by seat 42. With the valve connected and adjusted as desired, small changes in system fluid pressure will be allowed to vent through tube 38 and orifice 39 and the circuit through contacts 47 and 48 will remain open. When a system pressure increase larger than a preselected value occurs, orifice 39 will be sealed by seat 42 and the circuit contacts 47 and 48 will be closed. This condition will continue with no system fluid venting until the source of increased fluid pressure is removed.

Other adaptations and modifications of the apparatus of this invention will be apparent to those skilled in the art in view of the foregoing disclosure.

What is claimed is:

1. In a pressure relief valve and switch for selectively venting a pressure-sensitive fluid system and for indicating an increase in system pressure above a predetermined level, the combination comprising:

a valve body having a first passageway therein arranged for connection to a fluid system to be monitored;

a second fluid passageway in said body communicating with said first passageway, each end of said second passageway terminating at the surface of said body;

elastomeric diaphragms secured to said body over each end of said second passageway, said diaphragms being arranged to extend outward from said body in response to a fluid pressure in said passageway;

a third restricted fluid passageway connected at one end for communication with said first passageway and terminating at the other end adjacent and facing towards and closable by one of said diaphragms in response to said increase in system pressure; and,

an electrical contact assembly secured to said body and arranged to be actuated by outward movement of the other of said diaphragms.

2. The invention as claimed in claim 1 wherein said switch includes:

at least one electrical contact disposed adjacent and spaced from the unextended external surface of said expandable wall of said second chamber and directed thereat; and,

said external surface of said expandable wall of said second chamber including an electrically conductive portion opposite said contact.

3. The invention as claimed in claim 1 wherein said switch means includes:

a pair of electrical contacts disposed adjacent and spaced from the central portion of the external surface of said expandable wall of said second chamber and directed thereat; and,

an electrical conductor carried on the central portion of the external surface of said expandable wall of said second chamber, said conductor being arranged to complete an electrical circuit through said pair of electrical contacts in response to said predetermined increase in system fluid pressure.

4. The invention as claimed in claim 3 wherein said expandable wall portion of said second chamber is formed of an electrical insulator. 5

5. The invention as claimed in claim 4 including:

means for adjusting the spacing between said contacts and said conductor.

w i w: w w 

1. In a pressure relief valve and switch for selectively venting a pressure-sensitive fluid system and for indicating an increase in system pressure above a predetermined level, the combination comprising: a valve body having a first passageway therein arranged for connection to a fluid system to be monitored; a second fluid passageway in said body communicating with said first passageway, each end of said second passageway tErminating at the surface of said body; elastomeric diaphragms secured to said body over each end of said second passageway, said diaphragms being arranged to extend outward from said body in response to a fluid pressure in said passageway; a third restricted fluid passageway connected at one end for communication with said first passageway and terminating at the other end adjacent and facing towards and closable by one of said diaphragms in response to said increase in system pressure; and, an electrical contact assembly secured to said body and arranged to be actuated by outward movement of the other of said diaphragms.
 2. The invention as claimed in claim 1 wherein said switch includes: at least one electrical contact disposed adjacent and spaced from the unextended external surface of said expandable wall of said second chamber and directed thereat; and, said external surface of said expandable wall of said second chamber including an electrically conductive portion opposite said contact.
 3. The invention as claimed in claim 1 wherein said switch means includes: a pair of electrical contacts disposed adjacent and spaced from the central portion of the external surface of said expandable wall of said second chamber and directed thereat; and, an electrical conductor carried on the central portion of the external surface of said expandable wall of said second chamber, said conductor being arranged to complete an electrical circuit through said pair of electrical contacts in response to said predetermined increase in system fluid pressure.
 4. The invention as claimed in claim 3 wherein said expandable wall portion of said second chamber is formed of an electrical insulator.
 5. The invention as claimed in claim 4 including: means for adjusting the spacing between said contacts and said conductor. 